I perfectly understand the concept of the experiment, but a small doubt is haunting me. For example, if I run on different distances at same speed, it does not matter what direction I run, my speed will always be the same, nothwithstanding if I am moving against or with the travel of the earth through space. Evidently, if my speed was measured from outer space it would vary, it is normal galilean relativity. I understand Michelson-Morley experiment, but they performed this experiment on earth, at a building in Cleveland, they did not measure the rays of light from a view outside earth, so why were they expecting different measures if they knew that this light was supposedly travelling with the earth? I could understand if the test was performed on earth and someone from outer space took measures, but the fact that these measures were taken at earth confuses me; I know they expected different measures, but I dont see how since their reference was on earth! Probably is a very dumb question, as I am an only an attorney with interest in cosmology.